Temple Grandin says muscle fatigue provides a possible explanation for the worsening of the problem as beta-agonist fed cattle move through the handling and transport steps.

September 9, 2013

5 Min Read
Temple Grandin Explains Animal Welfare Problems With Beta-Agonists

There are certain groups of fed cattle that receive beta-agonists that have serious welfare problems at the packing plant. This problem became obvious to the industry when Lilly Edwards-Calloway from JBS showed a video of lame, stiff-gaited cattle at the National Cattlemen’s Beef Association (NCBA) summer meeting in early August.

Edwards-Calloway also stated that at least 20% of the cattle received at two JBS plants during hot summer weather were more difficult to drive out of the holding pens. She used words such as “tender-footed, lethargic, stiff, and no energy.”

 On the same day as the NCBA meeting, Tyson announced it would stop buying cattle fed the beta-agonist Zilmax™ because some animals at its packing plant were “unable to move and had difficulty walking.” Other major packers later announced they would no longer accept cattle fed Zilmax as well.

In my opinion, the cattle shown on the JBS video were suffering. Since the introduction of beta-agonists, I have made many similar observations. Many people called them anecdotal, but I have observed stiff gait and sore-footed walking in all four major types of fed cattle –Holsteins, Angus, Brahman crosses and mixed beef breeds with no Brahman influence.

Cattle okay at the feedlot but problems evident at the plant

Since the NCBA meeting, I’ve had discussions with people who work at both feedlots and packing plants. An obvious pattern has started to emerge.

First of all, some groups of cattle on beta-agonists are fine, while others have problems. A common problem is that while cattle may be fully mobile at the feedlot, they get progressively worse as they advance through the various handling and transport steps from the feedlot to the plant.


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Cattle may arrive at the plant with a stiff gait and, after having rested in the plant holding pens, become more reluctant to move. They act like they have both stiff muscles and sore feet.

A possible explanation for the worsening of the problem as cattle move through the handling and transport steps could be muscle fatigue. Zilpateral enhances the growth of “fast-twitch” fibers, a type of muscle fiber that fatigues more easily. A paper in the Journal of Animal Science (Baxa et al. (2009) 88:330-337) states that zilpateral feeding is associated with a transition away from slower fibers (slow twitch) to faster fiber types (fast twitch).

Both discussions and my observations indicate that when a problem occurs with beta-agonists, it is most likely to be associated with:

Hot weather.

• Zilpaterol – there are more problem cattle compared to ractopomine.

• Big cattle or heavy-muscled cattle.

• Uneven effects within the same lot of cattle. Half the cattle may be normal, and 5-10% severely affected. This may be due to uneven feed intake. Chris Reinhardt from Kansas State University presented data at the NCBA meeting that showed that 75% of cattle reduced feed intake on Zilmax, and 25% maintain the same feed intake. Another possible cause of problems may be poor feed mixing and some animals getting an overdose.

• Death loss during the late stage of feeding increased on beta-agonists, according to Guy Loneragen of Texas Tech University. He also presented at the NCBA meeting.

Why some feedlots don't have the issue

There are some very well managed feedlots that have been feeding beta-agonists and the cattle have had good mobility at the packing plant. Feedlots that have avoided problems may do the following:

• Sort cattle and avoid feeding beta-agonists to really large cattle. Do not feed it to cattle with health or foot problems. They sort on arrival and before feeding beta-agonist to create uniform groups.

• Careful feed mixing. Feed at the lower range of the 60 mg to 90 mg dose window per animal, which is listed on the label. Extensive testing of feed samples from the bunk. No top dressing.

• Add roughages to the diet. At one yard, adding an additional 3% more hay helped prevent problems. Another yard had 17% to 20% roughage in the finishing ration for beta-agonist cattle.

• During hot weather, handled cattle very early in the morning. During the summer, the cattle arrived at the packing plant in the morning when it was still cool.

• Practiced low-stress, calm cattle handling methods.

In conclusion, problems with stiff, sore-footed cattle must be stopped. The industry can’t allow stiff, lame cattle to become a new “bad becoming normal.” Two meat companies have already initiated scoring programs on incoming cattle for lameness and reluctance to move. I suggest the following simple scoring system for both feedlots and packing plants:

0 = Normal – Stands and walks normally, long confident strides, easy to move, vigorous. Beef breeds will have a definite flight zone unless reared in close confinement

1 = Mildly lame – Slightly stiff gait, sore-footed. Keeps up with normal cattle when the group is walking.

2 = Moderately lame – Lags behind and fails to keep up with normal cattle when the group is walking. Head down while moving, stiff gait, sore footed.

3 = Severely lame and reluctant to move – Limping, hard to move, reluctant to put weight on its feet. No flight zone and has difficulty moving. Handlers have to put their hands or driving aids on the animal to induce it to walk.

4 = Downed cattle – Includes cattle that are down and not able to stand, or exhibiting severe damage to hooves such as losing an outer hoof shell. I would also include standing “statue” cattle that refuse to move. Score 4 is more likely to occur at the packing plant.

It’s likely that in most groups of cattle fed beta-agonists those individual animals that score 3s and 4s at the packing plant will seldom be seen at the feedlot. At all stages of the handling and transport process, the percentage of mildly lame cattle should not exceed 10% scoring a 1. As an industry we must have high welfare standards.

Temple Grandin is a Colorado State University professor of animal science.


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